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题目：统计一个数字在排序数组中出现的次数，例如 {1,2,3,3,3,3,4,5}，3 出现了4次 。

代码解决

#include
   
    int s[8]={
  1,2,3,3,3,3,4,5};int findfirst(int x){    int left = 0, right = 7;    while(left <= right){          int mid = (left + right)/2;          if(s[mid] == x){             if((mid <= 0) || s[mid-1] != x) return mid;             right = mid - 1;          }          else if(s[mid] > x)            right = mid - 1;          else            left = mid + 1;    }    return -1;}int findlast(int x){    int left = 0, right = 7;    while(left <= right){          int mid = (left + right)/2;          if(s[mid] == x){             if((mid >= 7) || s[mid+1] != x) return mid;             left = mid + 1;          }          else if(s[mid] > x)            right = mid - 1;          else            left = mid + 1;    }    return -1;}void Print(int x){     int first = findfirst(x);     int last = findlast(x);     if(last ==-1 || first == -1) printf("%d 不存在\n",x);     else        printf("%d 出现了 %d 次\n",x, findlast(x) - findfirst(x)+1);}int main(){    int x = 3;    Print(x);    x = 5;    Print(x);    x = 6;    Print(x);}
   

结果